1. Field of the Invention
This invention relates to a bone joiner which is adapted to be attached to the surface of a bone across of the broken-away portion of the bone by means of screws or the like and is used to fix the broken-away portion, and particularly to a small bone plate suitable for joining cranial bones and facial bones.
2. Related Background Art
Bone plates formed with a plurality of fixing holes for inserting embedded screws into an elongated plate-like or ladder type body have heretofore been used as bone plates for fixing the broken-away portion of a bone such as the fractured portion of a bone or the excised portion of a bone in a coordinated state. These are generally formed of an inert material such as stainless steel, pure titanium or a titanium alloy, and are embedded in the human body for a long time or permanently. For the attachment of the bone plate, the bone plate is first positioned on the surface of a bone so as to stride over the broken-away line with the broken-away portion coordinated, and the positions of screw holes for embedding screws therein are determined. Screw holes are then formed at determined locations on the surface of the bone. Finally, the bone plate is again positioned on the surface of the bone, the embedded screws are inserted into the fixing holes and threadably inserted into the screw holes, and the bone plate is fixed to the bone.
Such bone plates of the prior art include relatively large bone plates used for fractured thighbornes or the like and small bone plates used for fractured facial bones, cranial bones, etc. They are, for example, Japanese Patent Application Laid-Open No. 53-146487, Japanese Patent Application Laid-Open No. 57-081333, Japanese Patent Application Laid-Open No. 63-186642, Japanese Patent Application Laid-Open No. 63-270044, Japanese Patent Application Laid-Open No. 1-190348, Japanese Utility Model Application Laid-Open No. 2-094515, Japanese Patent Application Laid-Open No. 2-503877, Japanese Patent Application Laid-Open No. 3-503020, etc. Of these, Japanese Patent Application Laid-Open No. 63-270044 includes a description of a microplate set particularly matching the three-dimensional shapes of the face and head. These publications include several proposals about the shapes of bone plates sufficiently fit for the surfaces of bones for inserting therein screws to be inserted into bones, in order to fix fractured bone portions reliably.
In these bone plates, however, it can be said that no sufficient measures are adopted for the operability when the bone plate is fixed to a fractured bone portion. For example, it is necessary to apply the bone plate to a fractured bone portion in advance and confirm the attachment position, and then form a mark or the like on the surface of the bone, and once remove the bone plate and form screw holes at locations on the surface of the bone which correspond to the fixing holes in the bone plate, and thereafter apply the bone plate again to the fractured bone portion and fasten it by screws. That is, according to the above-described prior-art bone joiner, it is difficult to position the bone joiner while holding the fractured bone portion in its coordinated state by one alone and moreover, it is necessary to determine the locations of the screw holes, and the working property thereof has been very inferior.
Particularly the microplate described in Japanese Patent Application Laid-Open No. 63-270044 is in itself so small that it makes one feel difficult to grasp it and therefore, requires a great effort in fitting the plate to an optimum location on a fractured bone portion. That is, in the case of a joining operation on the head and portions around it, such as cranial bones, the nasal bone and the jawbone, both of the fractured bone portion and the bone joiner are small and these are regions of the body which are difficult to support the bones and therefore, it is impossible to work quickly and appropriately.
On the other hand, Japanese Patent Application Laid-Open No. 3-057446 (U.S. Pat. No. 4,923,471) and U.S. Pat. No. 4,959,065 disclose a bone plate having a handle for gripping attached to the marginal edge portion thereof, and adapted to be positioned or fastened with the handle gripped in the work of fixing a fractured bone portion, the handle being removed after the fastening of the bone plate is completed. In this case, the work of positioning the bone plate and the work of fastening the bone plate become easy because of the presence of the handle. However, the work of forming screw holes must be done after the bone plate has once been removed, and during the work, the bone itself must be supported by other method (for example, a helper or other fixing tool). Also, such handle has its connected portion to the bone plate formed into a narrow neck and is adapted to be torn off after the bone plate is fixed to the fractured bone portion, but burrs may remain on the bone plate after the handle is torn off, they may injure the tissue around the fractured bone portion.